Attachable Micro-endoscopy System to Conventional Microscope for Live Mouse Organ Imaging using 4f Configuration Yoon Sung Bae1,2, Jae Young Kim3 and Jun Ki Kim1,2 1Biomedical Engineering Research Center, Asan Institute for Life Science, Asan Medical Center, Seoul, Korea 2University of Ulsan, College of Medicine, 88, Olympic-ro, 43-gil, Songpagu, Seoul, Korea 3Research Institute for Skin Imaging, Korea University Medical Center, Guro2-dong, Guro-gu, Seoul, Korea Keywords: Micro-endoscopy, Confocal Endoscope, Confocal Endoscopy, GRIN Lens. Abstract: The Micro-endoscopic technology combined with optical imaging system is essential for minimally invasive optical diagnosis and treatment in small animal disease models. Thus, the high resolution optical probe is required to achieve high resolution imaging. However, the optical imaging system requires highly precise and advanced technologies which are the main reasons for increasing system cost. Advancements in micro-optics and fiber optics technology have paved way in supporting compatibility among optical components. By providing compatibility between endoscopic system and existing conventional imaging equipment such as macro- or micro-scope, we could achieve in not only carrying out the high quality micro-endoscopic image procedure, but also reducing prices of the imaging system. The proposed system could be widely useful in the field of further biological study of animal disease model. 1 INTRODUCTION Karl Stortz, Mauna Kea Technologis and Olympus, the confocal endomicroscopy has higher resolution For the basic biology and preclinical study, the and enables minimum invasive. At the same time, experimental animal study is widely accepted for the confocal fluorescence system allows optical secure confirmation the biological hypothesis. sectioning of thick tissues. However, its highly However, the observation methods for in vivo precise micro-optical imaging system results in monitoring inside of the experimental animal are increasing system cost. Besides, conventional very limited. Micro-endoscopic technology makes it imaging microscopy from Leica, Zeiss and Olympus possible to visualize the inner cells and organs in etc. has limited working space and this is major small animal with in-vivo and minimal invasively. reason why the experimental mouse study could not As the technology of the optical fiber and micro- extend their applications into in vivo or live status. optics are developed, it has become essential In this work, the attachable micro-endoscopy system equipment for optical imaging diagnosis and is assembled based on commercialized confocal treatment in small animal disease models. fluorescence microscope by attaching the additional Recent advancement in micro-optics and fiber optics, optical components consist of 4f optical system, the miniaturized optical endoscopy probe, such as which relays the light path from the microscope to GRIN lens assembly or fiber-bundles is utilized in the endoscopy probe maintaining the optical the micro-endoscope. In addition to the technology, properties of the microscope. That expands the the high-resolution optical microscopy system is capability of the microscope, not only in-vitro, but also required for micro-endoscopes to achieve high- also in-vivo imaging as well. The micro-sized triplet quality imaging. GRIN(Graded-Index) lens probe is utilized to be One of the widely used micro-endoscopy imaging inserted into the body of the small animal placed on system is the confocal endoscope which enables us motorized translation stage. The colon and pancreas high-contrast and high-resolution, real-time imaging cells of mice are visualized by using the by taking advantage of the confocal system. implemented system for further biological study of Comparing with other commercial devices from animal disease model. 137 Bae Y., Kim J. and Kim J. Attachable Micro-endoscopy System to Conventional Microscope for Live Mouse Organ Imaging using 4f Configuration. DOI: 10.5220/0006101001370140 In Proceedings of the 5th International Conference on Photonics, Optics and Laser Technology (PHOTOPTICS 2017), pages 137-140 ISBN: 978-989-758-223-3 Copyright c 2017 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved PHOTOPTICS 2017 - 5th International Conference on Photonics, Optics and Laser Technology Figure 1: Illustration of the attachable micro-endoscopic system. (a) Junction part. (b) Relay optics part. (c) Endoscope holding part. 2 DESIGN OF ATTACHABLE Emission light from the sample goes back through the attachable micro-endoscopy system then, makes MICRO-ENDOSCOPE SYSTEM the images of the sample by the microscope. In order to compensate the imaging wobbling during 2.1 System Configuration rotational sample scanning process, the wobble stage is built in the holding part. The distance between Fig. 1. shows the schematic illustration of the endoscope and objective lens can be controlled using attachable micro-endoscopy system which consists Obj. Lens Z stage in Fig. 1. (c). of three parts, which are junction, relay optics and endoscope holding part. 2.2 4f System for Light Delivery Junction part depicted in Fig. 1. (a) connects the microscope to the endoscope for transmission of In order to deliver the lights between the microscope lights between the microscope and the endoscope and the probe of the endoscope, the 4f optical system probe. It is designed to be installed to the nosepiece is constructed in the relay optics part as shown in of the microscope and rotated for compatibility of Fig. 2. both upright and inverted microscope. The mounting adapter in the junction part is designed to accept the various threads of major microscope manufactures such as Leica, Zeiss, nikon and Olympus upright / inverted microscope etc. The illumination light from the microscope is reflected by the mirror in the junction part and passes through the relay part. Then the relay part delivers the light to the endoscope probe as shown in Fig. 1.(b). The delivered light is focused on the endoscope probe by the additional objective lens inside the Figure 2: 4f optical relay system consists of two lens and endoscope holding part, shown in Fig. 1. (c). mirror. 138 Attachable Micro-endoscopy System to Conventional Microscope for Live Mouse Organ Imaging using 4f Configuration Figure 3: (a) Triplet sideview GRIN lens probe; The triplet GRIN probe consists of two imaging lens and relay lens with micro-prism . (b) Micro-Endoscopy experimental setup combined with conventional confocal upright microscope. It extends the beam path of the microscope to the 0.35~1.0mm are mostly used for usual live mouse probe without loss of the lights power and changing imaging, since minimum invasiveness is very critical in the properties of the microscope. The system is in in vivo imaging. For the front-view probe, the utilized two lenses with same focal length, f . Those probe has no prism on the tip and this probe is more are distance 2 f each other and the objective mount appropriate for abdominal imaging for most organs. and objective lens are placed on the each sides of the Thus, front-view probe is more appropriate for system apart from f . It is well-suited for beam imaging most visceral organs such as liver, spleen, scanning microscopes such as confocal microscopes kidney and so on,. For the gastrointestinal and in which the endoscopy is attached in our study. The respiratory tracts such as colon, esophagus, trachea focal plane of the image is adjusted by translating and so on, side-view probe is more appropriate. the axial position of the objective lens. Thus, based on experimental purposes and directions, proper probes types, diameter and length should be 2.3 Endoscopy Probe and Complete chosen. System Fig. 3. (b) shows the attachable micro-endoscopy system built on the commercialized upright confocal Triplet GRIN lens is used as the endoscopy probe in microscope. The motorized translation stage is this micro-endoscopy system, which is connected utilized to place the sample animal and scan the the endoscope holding part. It should be noted that sample laterally. The micro probes are inserted into the other types of endoscopy probe can be joined probes hole and fixed on endoscope holder. The this system such as flexible fiber-bundles. Fig. 3(a) complete micro-endoscopy combined with the shows the triplet GRIN lens probe of side-view in confocal microscopy is applied for in-vivo which angled mirror prism is adhered on the tip of fluorescence cellular imaging of internal organs in a the imaging lens. The laser beam from the mouse. As a result, the experimental space has microscope goes through the probe then, forms a enlarged and system costs are reduced. focal spot in front of the prism, which scans the sample. The probe is inserted in the body of the animal to scan the cells in the organ. The emission 3 EXPERIMENTAL RESULTS light from the sample is collected by the probe and goes back to the microscope. The measured lateral and axial resolution of the There are several kinds of probe diameter from attachable micro-endoscopy system are 1μm and 0.35mm to 2.8mm. However, the probes of 10μm, respectively within 300μm of field of view, 139 PHOTOPTICS 2017 - 5th International Conference on Photonics, Optics and Laser Technology when diameter of 1mm probe is used. That shows ACKNOWLEDGEMENTS sufficiently high-resolution of the system for application of cellular imaging of mouse. The This work was supported by the Basic Science optical penetration depth of a GRIN probes is Research Program [2014R1A1A2057773, limited to about 100μm in most organ tissue. 2015K2A7A1035896] through the National Fig. 4 shows the images of the cells in anesthetized Research Foundation of Korea (NRF) funded by the mouse organs taken by our system. We visualized Ministry of Science, ICT & Future Planning and by the mouse colon vasculature image after Acridine a grant (2015-641, 2015-646, 2016-7212) from the Orange IV injection. Fig. 4. (a), and (b) are the Asan Institute for Life Science, Asan Medical fluorescence image of mouse clone which clearly Center, Seoul, Korea.